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The rheological properties of fresh cement paste with different amount of ultrafine circulating fluidized bed (UCFB) fly ash was fitted through the rheological models. The results show that the fresh cement paste containing different content of UCFB is always Bingham fluid. When the content of UCFB fly ash was lower than 30 wt%, the rheological properties of cement-UCFB fly ash were better than that of pure cement paste. In addition, when the amount of UCFB fly ash was 10 wt%, the fresh cement-UCFB paste has the best rheological properties. The effects of particle size distribution on the rheological properties of cement-UCFB paste were also analyzed through Rosin-Rammler fitting analysis. The packing density and particle size distribution are the main factors affecting rheological properties of the system. When n value is smaller, in other words, the particle size distribution range is wider, the fluidity of cement-UCFB fly ash system is better than that of pure cement. The morphology of the particles also affect the rheological of the fresh cement paste.

The pozzolanic activity of ultrafine circulating fluidized-bed (CFB) fly ash prepared by jet mill has been investigated in this research. The ultrafine powder properties and the hydration heat release process of the cement blended with ultrafine CFB fly ash have been obtained. Furthermore, the dissolution characteristics of SiO2 and Al2O3, the Ca2+ absorption capacity in saturated Ca(OH)2 solution, and the polymerization degree of Si-O and Al-O polyhedrons have been studied to further clarify the mechanism of ultrafine grinding on pozzolanic activity. Compared to raw CFB fly ash (RCFA), the particle morphology, the pore structure of ultrafine CFB fly ash (UCFA, D50 ≤ 5 μm), and the pozzolanic activity of UCFA are significantly improved. The hydration rate of cement blended with UCFA is accelerated, and the total heat release is close to that of pure cement within 72 h. Ultrafine grinding increases the SiO2 and Al2O3 dissolution rate of CFB fly ash and Ca2+ absorption capacity in saturated Ca(OH)2 solution, mainly due to the decrease of polymerization degree of Si-O and Al-O polyhedrons and particle size of CFB fly ash.

This paper investigated the rheological properties of cement paste containing high volume circulating fluidized bed fly ash (CFBFA) using a rheometer. The effects of fly ash (type, content, particle size distribution and surface characteristics) on the rheological parameters of the cement paste were analyzed. The test results showed that the rheological properties of the paste system exhibited Bingham fluid characteristics when the replacement level of cement by CFBFA (d50 = 56 μm) was less than 50%. When the content reached to 70%, the rheological properties were exhibited the characteristics of revised-Bingham fluid model. In contrast, the cement with ultrafine CFBFA (d50 = 5 μm) exhibited the fluid characteristics that follow the Herschel-Bulkey model. The results also showed that the particle size distribution and the surface characteristics of fly ash were the important influencing factors on the rheological parameters, where particle size distribution played a decisive role. Results from the Rosin-Rammler fitting analysis showed that the use of CFBFA would increase the d50 value of paste particles and widen the particle size distribution. When the content of CFBFA was 50%, the yield stress and plastic viscosity of the paste system were increased by 76% and 169%, respectively, however the fluidity of the paste system was lowered. On the other hand, the use of ultrafine CFBFA would reduce d50 value and narrow the particle size distribution. Owing to the ultrafine particles of FA3, the thixotropy of the paste increased when the content of ultrafine CFBFA in the paste was low. When the content of ultrafine CFBFA was 50%, the yield stress and plastic viscosity of paste system were reduced by 45% and 54%, respectively, and the fluidity of system was improved.

This paper investigated the effect of organic compounds with ester groups on the hydration and hardening of cement. The effects of five kinds of organic compounds with ester groups (ethyl acetate, dimethyl oxalate, glyceryl triacetate, trimethyl phosphate, and triethanolamine borate) on hydration heat, hydration degree, setting time, mechanical properties, microstructure, and pore structure of hardened cement slurry were studied. The test results showed that esters can make the end time of cement hydration induction longer and delay the occurrence of the second exothermic peak. Also, the effect of five kinds of esters on the hydration and hardening of cement was basically followed by TG> TB> DMO> EAC> TMP. In terms of molecular structure, for organic compounds containing only ester groups, the higher the number of ester groups, the greater the effect on the hydration of cement. The introduction of other functional groups (such as phosphate or borate) will influence the effect of the esters.

The coal was sampled from No.15 coal seam in coalfield of southeast Shanxi. The Hg, As, Se, Cr and Pb occurrence in coal seam and environmental features of the heavy metal elements of coal were studied by X-ray fluorescence spectrometry (ARL Quant 'X), X-ray diffraction (XRD) and inductively couple-plasma mass spectrometry (ICP-MS). Environmental features, such as heavy metal element concentration, distribution and occurrence mode, etc., were studied by systematic determination of element concentration, inorganic element and mineral composition in coal. The results showed that the coal from No.15 coal seam had the mercury (Hg) concentration between 0.44 and 0.268 μg/g, and average Hg concentration of 0.11 μg/g; arsenic (As) concentration between 0.31 and 0.91 μg/g, 0.61 μg/g on average; selenium (Se) concentration between 0.94 and 3.56 μg/g, 2.45 μg/g on average; chromium (Cr) concentration between 9.54 and 24.58 μg/g, 17.06 μg/g on average; lead (Pb) concentration between 10.23 and 23.56 μg/g, 18.13 μg/g on average. The comparison with the Clark value showed Se was significantly enriched, As and Cr were lost, and Hg and Pb were normal. Compared with the coal from other counties and regions both at home and abroad, as was lost and other elements were normal. The elements irregularly distributed vertically. In spite of different element concentrations in adjacent coal seams, no significant enrichment occurred. The target elements mainly occurred in the form of inorganic matters except As. Hg was mainly concentrated in pyrite and clay minerals. Se, Cr and Pb were mainly concentrated in kaolinite, and Se was mainly concentrated in illite. Because of different occurrences or different forms in one mineral, the Hg, As, Se, Cr, and Pb loss rates were 99.43%, 85.91%, 77.89%, 73.81%, and 68.85% at 815°C, respectively.